language_models: Update tiktoken-rs to support newer models (#30951)

I was able to get this fix in upstream, so now we can have simpler code
paths for our model selection.

I also added a test to catch if this would cause a bug again in the
future.

Release Notes:

- N/A
57424e4743Ben Brandt committed on 5/19/2025, 11:40:36 AM· committed by GitHubparent2b6dab9
3 files changedLine totals unavailable